1. Field of the Invention
The present invention relates to a quasi wide-angle zoom lens, having a zoom ratio of approximately 2, for a digital camera or video camera or other cameras, in which an image is formed on a solid state image pickup device (CCD).
2. Description of the Related Art
A zoom lens consisting of a first negative lens group and a second positive lens group is known in the art of quasi wide-angle zoom lenses (focal length being in the range of approximately 43 to 86 mm in terms of that of a lens for 35 mm format). In the known two (double)-lens-group zoom lens, since a diaphragm is provided in or near the second lens group and is moved together with the second lens group, it is impossible to increase the distance between an exit pupil of the entire zoom lens system and an image forming surface, particularly at the wide-angle extremity, and hence the known two-lens-group zoom lens is not useful for a CCD camera. This is because, in a CCD camera, telecentricity of the zoom lens in which light emitted from the lens is incident on the CCD at almost right angles is preferred to ensure a uniform or regular color.
Moreover, the movable diaphragm increases the manufacturing cost of the lens frame structure. Furthermore, a large negative distortion occurs particularly near the wide-angle extremity, due to the arrangement of the negative and positive lens groups on opposite sides of the diaphragm.